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Peter Anvin" CC: Alexander Graf , Boris Ostrovsky , Subject: [RFC PATCH 08/56] x86/bugs: Reset SSB mitigations Date: Mon, 13 Oct 2025 09:33:56 -0500 Message-ID: <20251013143444.3999-9-david.kaplan@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20251013143444.3999-1-david.kaplan@amd.com> References: <20251013143444.3999-1-david.kaplan@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: satlexmb07.amd.com (10.181.42.216) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN1PEPF0002BA50:EE_|DM4PR12MB5889:EE_ X-MS-Office365-Filtering-Correlation-Id: 567f09a5-14cf-4c4f-f336-08de0a65be6a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|36860700013|82310400026|1800799024; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?D/Ksy72QndHDpyNAF1UdN9xAUt6qj569xysPYe68cyprl31srSttp1xC8WOZ?= =?us-ascii?Q?fycowzxzTQuRG+MxAXCB5NdURlPcMGgnMlImTP5YYIipMpXooCrNVihxHfUA?= =?us-ascii?Q?Y1B6jNJ9/zDzi/C7YUo8xI9o/EjUMdpkOBu6U7IKndbhZj20vC5feXTXEeI9?= =?us-ascii?Q?zkvZhJJSTeMSEd7B8QIndyAsaKzBpFY4V86U+QIbDLNpnNyjBSb7i9DsI5Tg?= =?us-ascii?Q?HqoEAUYzJrC92V1xdT1qBBlMGDBYTOKYgRCWdz9W498wK70+KcngxI8dPzex?= =?us-ascii?Q?6fYU3UwR+b6c8nOmN2ADqjXgacy0S0SizmQ/flq2U+EWfHRtMjX2LtlvjOgI?= =?us-ascii?Q?V9F7VWonKlYmtDIWefv0Z9H4eJS5p8Hqs7NtrXU09a+LpOx6Ma9+xqNhTRO7?= =?us-ascii?Q?BtScsFRcOzAHfumppP/pGVzPyPj4JBPsiKW3HO3ExvRI1kz+3hq31TpoGUgC?= =?us-ascii?Q?b6zksWKg5w+Nhs2eBZ/gBz3xc97V7qoT86k2exrkp3M3GAzEln126ewPrQEs?= =?us-ascii?Q?EGC2HWwI7EOOz0XituASN7Nl0zFgNll0gN2vpSRalVOAB33JxSdAmg9AzKgR?= =?us-ascii?Q?jBYyHoFvTyX1DGpoRNNW43Uji0xOzwnxzQ6f8yRaxab6M3bkI6gn7PMjNqAV?= =?us-ascii?Q?GOScdX4zhjzay7XWUr4eYv2rtifIf0kiyDJo7N2OLwmuBcJ+zdtB/7L3I8DZ?= =?us-ascii?Q?VIFDhVpRbd0HYK1yF5M9AqgLszJ1FTxnxkCFM4taGxtZRZ99dcaa0avRG5vp?= =?us-ascii?Q?0/UgqUIp4A2N4R8XplqJOvD+kFgFJoAPAGrCf14wlpV8xNM12ujpeDrdn7h0?= =?us-ascii?Q?kg0n90iPog+9P/SMgq0Vtwe7TvZi+wL9mbxoPGflancLuYOuiHHVRpgRbr2o?= =?us-ascii?Q?00M0asVDwttvOs9V892tpRMJfbuTrVDGJpSSDjPbCiKXjgdKuxKApEI0cS1T?= =?us-ascii?Q?eMoa9Ws2sThAE+Y1LrEcWm8mgdJy2zeD7SIV9eCaAHSaUiuFdHsrIJfv+0mk?= =?us-ascii?Q?3O1t7WBfvBCxch6AwyJfbqI09BuciZ8i/gHXcqbjg5ung/nQc7O8F8vD6QDS?= =?us-ascii?Q?nNNxYDtANCkLV4XxeIazA3WAvQqsurD45h9ie7a/O/D59e4miVxu2aGv+6lm?= =?us-ascii?Q?AjxsrlrjlqscVMrSZmsTZTC+73iY991Rs2zYZwoo0gCAJ2SdRdSXoAQ5jNzG?= =?us-ascii?Q?xSpiVjqKKMSCSINfEpyh9QxYrgTMEUfO+/iP/Ona4EWgj6ZipENpYmW73ad6?= =?us-ascii?Q?xgsy1n4tkg8Dtpg7xHspqBqjfJSloVL/qNPAgfUY+9HXqo0Tc/3siUjbc4vo?= =?us-ascii?Q?Obo759r2WlH9/UIm0bnIfLyfeAb0vSPVSdkMjasf1lREp12U8gIqj6PvffVS?= =?us-ascii?Q?WLhzCdME+/LW69HdBGoXdKe28zhQDO5PHbO1Njo7Be+sQeFZRkU/UcnyjfGb?= =?us-ascii?Q?CR12mBkQfHSiGeL84NZ8jjg8ob51hL4Cccej4ygMaMlFxYFJHdTHz7npZNnS?= =?us-ascii?Q?Z7acF1xWiGcTO6yAzSgsRqmK1GqIFmr6+dgLKNaOGHY8YSet4HPz4jg5MLtw?= =?us-ascii?Q?0P/PuRTKNJ0z7GLMAkQ=3D?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(7416014)(376014)(36860700013)(82310400026)(1800799024);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Oct 2025 14:35:23.5190 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 567f09a5-14cf-4c4f-f336-08de0a65be6a X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SN1PEPF0002BA50.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB5889 Content-Type: text/plain; charset="utf-8" Add function to reset SSB mitigations back to their boot-time defaults. Signed-off-by: David Kaplan --- arch/x86/kernel/cpu/bugs.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 4ca46f58e384..cc7b1b67d22d 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -380,6 +380,16 @@ static void x86_amd_ssb_disable(void) wrmsrq(MSR_AMD64_LS_CFG, msrval); } =20 +static void x86_amd_ssb_enable(void) +{ + u64 msrval =3D x86_amd_ls_cfg_base; + + if (boot_cpu_has(X86_FEATURE_VIRT_SSBD)) + wrmsrl(MSR_AMD64_VIRT_SPEC_CTRL, 0); + else if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD)) + wrmsrl(MSR_AMD64_LS_CFG, msrval); +} + #undef pr_fmt #define pr_fmt(fmt) "MDS: " fmt =20 @@ -2672,6 +2682,17 @@ static void __init ssb_apply_mitigation(void) } } =20 +#ifdef CONFIG_DYNAMIC_MITIGATIONS +static void ssb_reset_mitigation(void) +{ + setup_clear_cpu_cap(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE); + x86_spec_ctrl_base &=3D ~SPEC_CTRL_SSBD; + nossb =3D false; + ssb_mode =3D IS_ENABLED(CONFIG_MITIGATION_SSB) ? + SPEC_STORE_BYPASS_AUTO : SPEC_STORE_BYPASS_NONE; +} +#endif + #undef pr_fmt #define pr_fmt(fmt) "Speculation prctl: " fmt =20 @@ -2916,6 +2937,8 @@ void x86_spec_ctrl_setup_ap(void) =20 if (ssb_mode =3D=3D SPEC_STORE_BYPASS_DISABLE) x86_amd_ssb_disable(); + else + x86_amd_ssb_enable(); } =20 bool itlb_multihit_kvm_mitigation; @@ -3857,5 +3880,6 @@ void arch_cpu_reset_mitigations(void) spectre_v2_reset_mitigation(); retbleed_reset_mitigation(); spectre_v2_user_reset_mitigation(); + ssb_reset_mitigation(); } #endif --=20 2.34.1